1. Field of the Invention
The invention relates to a rack shaft supporting device that supports a rack shaft with the use of a support yoke, and a steering system including the rack shaft supporting device.
2. Discussion of Background
A steering system described in US 2010/0024583 A1 includes a support yoke, a plug, an intermediate component, and a torque generation spring. The intermediate component is located between the support yoke and the plug. The intermediate component has intermediate cam faces.
The plug has plug cam faces. The plug cam faces make surface contact with the intermediate cam faces. The torque generation spring is arranged in a space surrounded by the plug and the intermediate component. One end of the torque generation spring is attached to the plug, and the other end thereof is attached to the intermediate component. The torque generation spring applies, to the intermediate component, a force for rotating the intermediate component relative to the plug.
In the rack shaft supporting device, a force of friction between the plug cam faces and the intermediate cam faces serves as a resistance to the force that is applied by the torque generation spring to rotate the intermediate component relative to the plug. Further, in order that the intermediate component rotates relative to the plug smoothly, it is preferable that a force of friction between the plug cam faces and the intermediate cam faces be small. However, in the rack shaft supporting device, the plug cam faces make surface contact with the intermediate cam faces. Therefore, there is still room for improvement from the viewpoint of reduction in the force of friction between the plug cam faces and the intermediate cam faces.